Iranian Journal of Plant Protection Science
Year:2011 | Volume:42 | Issue:1|Papers Count:18

Melon ladybeetle, Epilachna chrysomelina (F.) is one of the most injurious cucurbit attacking pests. Sampling program and host preference of this ladybeetle were studied in Ahvaz, Southwest Iran. Suitable sample size, suitable location for sampling as well as suitable sampling life stage of the insect were obtained to be 12 on, lower leaf surface and egg stage of the ladybeetle, respectively. E. chrysomelina preferred cucumber to other host species under laboratory conditions. Two preference experiments were conducted under field conditions. During the first experiment, the preferences of E. chrysomelina to cucumber and marrow (two most preffered hosts in the laboratory experiment) were evaluated. In the second experiment preference of the ladybeetle to different cucumber cultivars (Prince, Superdominus, R S Fronto as well as Syrana) was arranged in a split plot (in time), employing a completely randomized blocks design of four replications. In the course of the first experiment the mean total population at different developmental stages of E. chrysomelina was found to be higher on cucumber than on marrow from early till late June. As for the second experiment the mean total population at different developmental stages of the ladybeetle was significantly higher on Superdominus cultivar than on the other cultivars tested. So, it is recommended that in the areas suffering from high populations of this pest, cultivation of Superdominus variety be either avoided or it is cultivated as a trap crop along with the other control measures employed to suppress the pest, melon ladybeetle.

Fanleaf degeneration, a disease caused by Grapevine fanleaf virus (GFLV), is considered as the most destructive grapevine viral disease worldwide causing severe losses in vineyards, annually. GFLV is apparently believed to have originated from ancient Persia and therefore, to restrict it in its further infections, a precise identification along with a monitoring of its distribution pattern is crucial. Distribution and relative rate of infection to GFLV in vineyards and nurseries from some different parts of Iran was studied. A total of 882 cuttings were collected from Karaj, Bavanat, Shiraz, Jahrom, Maymand, Ourmia, Naghadeh and Abhar. Infection was confirmed in 204 samples using such different diagnostic methods as mechanical transmission to test plants, as well as serological and molecular techniques. Results confirmed GFLV infection in some new regions of Iran for the first time, including some nurseries in Karaj and some in Naghadeh city. The most severely infected samples were observed in Bavanat, while 63.7 percent of the samples being infected. No infection was detected in Abhar city. Infection varied from 1.8 to 43.1 percent in the other regions. Results proved widespread distribution of GFLV races to different regions of Iran, confirming the fact that it had been spread from its believed origin through infected cuttings and scions.

A faunestic survey of the euoribatid mites of Shendabad region (East Azerbaijan Province, Iran), was carried out during three different times of the year 2008 (mid-July, mid-August as well as mid-September). By use of the Berlese funnel, the mites were extracted, cleared in Nesbitt’s fluid following which microscopic slides were prepared. During the study, 31 species belonging to 21 genera, 13 families, and 8 superfamilies were collected and identified within 2500 specimens, of which four genera, two subgenera and five species related to mite fauna of Iran while three families, two genera and six species for mite fauna of the Province are new records and which have been marked with two vs. one asterisks (*), respectively, and as follows:Metabelba* (M.) pulverulenta**, Parabelbella* (Tectodamaeus**) sp. (Damaeidae*); Berlesezetes brazilozetoides*, Microzetes**(M.) baloghi**(Microzetidae); Fosseremus quadripertitus*, Damaeolus*ornatissimus*(Damaeolidae); Liacarus (L.) brevilamellatus*, Liacarus (L.) xylariae**, Liacarus (Stenoxenillus**) sp. (Liacaridae); Xenillus*(X.) setosus**(Xenillidae*); Ceratoppia*quadridentata*(Ceratoppiidae*); Tectocepheus velatus, Tectocepheus minor (Tectocepheidae); Ramusella (Ramusella) puertomonttensis, Anomaloppia iranica, Rhinoppia obsoleta, Rhinoppia subpectinata*, Microppia minus, Oppiella nova (Oppiidae); Epimerella*sp. (Epimerellidae*); Lucoppia**orientalis**, Oribatula (Zygoribatula) debilitranslamellata, Oribatula (Z.) skrjabini, Oribatula (Z.) undulata, Oribatula (Z.) connexa connexa, Oribatula (Z.) connexa ucrainica, Oribatula (Oribatula) pallida, Oribatula (O.) tibialis*allifera*(Oribatulidae); Protoribates (Protoribates) paracapucinus, Sicaxylobates**sp. (Protoribatidae); Liebstadia (Liebstadia) similis (Liebstadiidae); Psammogalumna**sp. (Galumnidae).

Some yeast species play important roles in biological control of some fruits’ post harvest infections. For instant, Candida, Rhodotorula and Pichia species employed in biological control of such post harvest diseases as blue mold (Penicillium expansum), and also grey mold (Botrytis mali) in apple. Species identification of yeasts is some most essential part of the related research activities. Due to various problems arising in the routine processes of morphological and physiological identification techniques, DNA- based methods have recently been constructively developed. In the present study 32 yeast strains were isolated from several apple cultivars. The ITS1 and ITS2 regions of the isolates were separately amplified and the isolates grouped as based on Fragment Size Polymorphism (FSP) of the amplicons. Based upon a comparison of the electrophoretic patterns of PCR products with Rhodotorula mucilaginosa, obtained from CBS as a standard, the isolates’ species were identified as Rhodotorula. For a precise final identification, the ITS-PCR products were subjected to sequencing followed by Blast Analysis. As a result, four isolates were detected as belonging to Rhodotorula genus from which three were identified as R. musilaginosa while one as R. glutinis. It becomes evident that the method PCR- FSP in combination with some other approaches is helpful in identification of Rhodotorula species.

Host Plant's quality in the food chain of a herbivorous insect influences the insect's life performance, and thus abundance in its population. The effect of different ratios of N: K fertilization (40:60), (40:40), (40:0) kg/ha vs. control (0:0) were determined on chemical content parameters (N, K and C %) of the bean plant and as well on the performance of Aphis fabae Scop. Experiments were carried out in a greenhouse with 25±1oC, 75±5 RH and a photoperiodism cycle of 16 L: 8D hours. The highest percentages in plants tissue of N and K were found in plants fertilized with 40:0 and 40:60 (N:K) ratios respectively. Net reproductive rate (R0) of A. fabae fed on the mentioned treatments were determined as 14.75±2.4, 20.27±1.38, 22.07±2.2 and 17±3.1 female/female/generation, respectively. Intrinsic rate of increase (rm) of A. fabae on the four treatments were assessed as 0.215±0.017, 0.325±0.02, 0.295±0.014 and 0.258±0.017, respectively. Finite rates of increase (l) amounted to 1.32±0.001, 1.41±0.03, 1.38±0.01 and 1.32±0.001, respectively showing the daily rate of increase in aphid female population relative to that during the previous year. Mean generation times (T) in the four treats were 12.51±0.17, 9.32±0.17, 10.48±0.16 and 10.19±0.14 days. The results showed that there existed significant differences between R0, rm and l of A. fabae different treatments (P<0.05). The highest rm and R0 were observed in treatments N: K with ratios of 40:40 and 40:0 showing that these treatments result in the most suitable best host plants for growth and development of A. fabae.

Wheat leaf rust (Puccinia triticina Eriksoon) is of the most injurious wheat diseases that prevails throughout areas where wheat is grown. An identification of virulence factors along with differences in the population of pathogen in different wheat growing regions is necessary for an enhancement of resistant cultivars with effective resistant genes to leaf rust. To accomplish the purpose, a leaf rust Trap Nursery containing 37 near isogenic lines in addition to Bolani susceptible cultivar as check were planted under natural infection conditions in Gorgan (with an application of mist irrigation) and Gonabad (with no mist irrigation) locations during 2002-2007. Reaction to the disease of each line was recorded at the flag leaf stage and when infection on the Bolani susceptible cultivar was at its maximum level for infection rate and type. "S" reaction indicated virulence while "O, R, MR and MS" reactions were indicative of as avirulence. Results showed that virulence was detected for genes Lr1, Lr2c, Lr3, Lr3ka, Lr3bg, Lr10, Lr11, Lr12, Lr13, Lr14a, Lr14b, Lr15, Lr16, Lr17, Lr18, Lr20, Lr21, Lr22a, Lr22b, Lr23, Lr24, Lr26, Lr30, Lr32, Lr33, Lr34 and either Lrb at one or both Gorgan and Gonbad locations. Virulence was observed for genes Lr3, Lr10, Lr14b, Lr17, Lr18, Lr26 and Lr34 only at Gorgan site. No virulence was observed for genes Lr2a, Lr2b, Lr19, Lr25, Lr28, Lr29, Lr35, Lr36 and Lr37 at these locations. Avirulence due to the resistance of the above resistant genes provides the possibility of the use of these genes in breeding programs to develop varieties resistant to wheat leaf rust.

To study the population structure of Gibberella fujikuroi species complex, the causal agent of rice foot rot, samples were taken from different rice growing regions of Guilan province in 2004. Among fourty-one isolates recovered from different cultivars; three isolates did not produce microconidial chain. In order to study the sexual fertility and determine the mating type as well as mating population among isolates, each isolate was crossed with six female tester isolates from three known mating populations of A, C and D on Carrot Agar (CA) medium. Two tester isolates from two opposite mating types including MATA-1 and MATA-2 for mating population A, MATC-1 and MATC-2 for mating population C as well as MATD-1 and MATD-2 for mating population D were taken to pair with Iranaian isolates. As a result, ten isolates in mating population A (Fusarium verticillioides), two isolates in mating population C (F. fujikuroi) and twenty-nine isolates in mating population D (F. proliferatum), were grouped. All the F. verticillioides and F. fujikuroi isolates belonged to MATA-1 and MATC-1 mating type, while both MATD-1 and MATD-2 mating types were identified among F. proliferatum isolates. Because of the presence of both mating types among mating population D isolates, mating possibility was studied among them. Among thirty-six crosses between these isolates, only two led to formation of perithecium containing ascospores. Vegetative compatibility tests revealed that ten F. verticillioides isolates belonged to nine Vegetative Compatibility Groups (VCGs), two F. fujikuroi isolates were grouped in two distinct VCGs each with one member and twenty-nine isolates which belonged to F. proliferatum were divided into twenty VCGs. In complementation tests among nit mutants of isolates the isolates belonging to three mating populations failed to form heterokaryons. Pathogenicity test related to fourty-one isolates was done on the susceptible cultivar Khazar in which all the isolates caused disease symptoms with white colonies on the stems. In this investigation it was demonstrated that all the three mating populations A, C and D from G. fujikuroi species complex were the causal agents of rice foot rot in Guilan paddy fields. Moreover, based on vegetative compatibility tests, each of the mating populations A and D showed high genetic diversity, the existence of several single-member VC groups confirming this conclusion.

Tetranychus urticae Koch is an injurious pest of, fruit crops, crop plants as well as ornamental plants worldwide. The high reproductive potential of T. urticae and its fairly short life cycle along with the frequent application of acaricides usually required to maintain T. urticae populations below economic thresholds, facilitates the pest's resistance to acaricides, and consequently control failures. In the course of the present study, the resistance mechanisms of two-spotted spider mite, Tetranychus urticae, to abamectin was surveyed. Bioassay tests were carried out through leaf dipping in a toxic solution method using formulated abamectin (25 EC). The LC50 for resistant population could not be exactly figured out due to phytotoxicity of abamectin at its high doses (>3100 ppm), with resistance ratio to abamectin being over 3000 fold. Enzyme assays revealed that esterase activities in the resistant population were 2.14 and 1.33- times higher than those in the susceptible ones where a-naphtyl acetate (a-NA) and a-naphtyl propionate (a-NP) were used as substrate, respectively. Estimation of kinetic parameters and the amount of glutathione S-transferase activity also indicated the significant difference between the two populations; since enzyme activity in resistant population was 1.71 folds that in susceptible population. Also Km and Vmax values of resistant population (on CDNB substrate) were 1.43 and 1.15 times lower vs. higher than those in susceptible population, respectively. Furthermore, the results showed that the level of cytochrome P450 in resistant population was 1.37 times that in susceptible population. Considering the high resistance ratio, in addition to metabolic resistance, one of the other resistnce mechanisms very likely is the target site becoming more and more insensitive.

The interaction between root-colonizing Pseudomonas fluorescens strain CHA0mcherry and three wheat cultivars (Bolani, Roushan, Forno) was studied as a phenomenon to be employed in the control of Wheat Leaf Rust Disease (Puccinia triticina). CHA0mcherry was inoculated using seed treatment method. The application of CHA0mcherry reduced the number of pustules on leaves via inducing systemic resistance, specially in Bolani cultivar. The non-inoculated Bolani and Forno cultivars exhibited the highest infection of the leaf rust. A study of the bacteria-wheat-pathogen interaction indicated that Forno was the most responsive root- colonized variety to the bacterium. The lowest colonization was observed within the rhizosphere of Roushan cultivar. Interaction between pathogen and cultivars was shown to lead to increase of peroxidase and Phenylalanine Ammonia Lyase (PAL) activity in leaves. In summary, the results showed negative correlations between the bacterial colonization (cfu per mg dry root) and the number of rust pustules on the leaves. There was also a significant correlation noted between PAL activity and disease severity.

Prey preference of natural enemies is among the phenomena that should be considered in determining the efficacy of natural enemies. When the predators are faced with a choice between two or more preys, they often show their preference to one from among them. Temperature is one of the environmental factors that can affect insect foraging behavior. Two aphid species namely Aphis fabae and Acyrthosiphon pisum are of the ability to attack and damage bean plants. Prey preference of Iranian native species Hippodamia variegata as one of the efficient aphid predators, was examined on bean plants and on the two named species of aphids at different temperatures. The experiment was carried out at 15±1oC, 19±1oC, 23±1oC, 25±1oC, and 27±1oC, plus 70±10% of RH, and a photoperiodism state of 16:8 (L:D). Predator preference was analyzed through an application of Manly’s index of preference to the data with statistical analysis showing that at all temperatures for fourth instar larvae, male and female (except 15oC for the fourth instar larvae), A. fabae was preferred to Acyrthosiphon pisum. This experiment showed that H. variegata does not change its preference in response to temperature and it is assumed that at variable conditions of releasing the same trend be affected.

An experiment was carried out in 2008-2009 to study the correlation between the reaction to potassium chlorate and pathogenicity on some Iranian isolates of Macrophomina phaseolina, the causal agent of soybean charcoal rot. From among a total of 48 collected isolates from the major soybean cultivation areas of Golestan, Mazandaran, Ardabil, and Lorestan provinces, twenty four isolates were selected as representative their geographical origins. The isolates were cultured on Minimal Medium of 120 mM potassium chlorate. Five isolates (about 20%) were chlorate sensitive while 19 (about 80%) chlorate resistant. Pathogenicity test was carried out under in vitro (through seed inoculation) as well as under greenhouse (stem and soil inoculation) conditions. In any of the three tests, all the studied isolates were pathogenic to the soybean cultivar Williams. Mean comparison of treatments showed highly significant differences (p<0.01) among virulence of isolates. Moreover, in in vitro as well as in the greenhouse test of the stem inoculation, sensitive to chlorate isolates were less virulent on seeds and stems of the soybean sensitive cultivar Williams, whereas in greenhouse test involving soil inoculation, a higher level of pathogenicity was observed in sensitive to chlorate isolates in comparison with the other tests. According to the obtained results it seems that the inoculation method can affect the correlation between sensitivity to chlorate and pathogenicity as regards from soybean isolated Macrophomina phaseolina.

An ability of the fluorescent pseudomonad bacteria is to secrete such secondary metabolites as hydrogen cyanide, protease, salicylic acid as well as siderophore which prevent the growth of soil-habitant pathogens. Tests were done for evaluating the materials produced by the said bacteria. In the tests' cultures, P. aeruginosa strains 7NSK2, UTPF92, and UTPF86 produced the most hydrogen cyanide, protease, and salicylic acid respectively. The said strains caused the most parasitism on second-stage larvae (more than 70%) as well as parasitism on nematode egg (more than 60%) in vitro (bacterial suspension against nematode in 96-well basins) (P£0.01). Three-week-old wild type tomato seedlings were planted in plastic pots (8 cm diameter) filled with 300 g unsterilized sandy-loam, and transferred to a glasshouse. After one week, the plants were treated with bacteria by adding 30 ml of the bacterial suspension (1.9-2.1×109 CFU/ml) into soil around the root system. Control plants received 30 ml of one-fourth concentration of Ringer Solution. Two days after bacterial application, 2000 freshly hatched juveniles of M. javanica were added to the soil by making three holes around the seedlings. After 45 days past, some growth indices (dry weight of the aerial parts and root, the wet weights of the aerial parts, root and stem lengths) as well as disease indices (gall number and diameter, nematode population in soil and root along with bacteria endophyte population) were assessed. The study was arranged on the basis of a completely randomized design of ten treatments and five replications. In the roots inoculated by P. aeruginosa 7NSK2 and UTPF86 strains the most increase in total plant-growth (63% increase) was observed along with least the nematode penetration (55% decrease) into root accompanied by least gall formation (53% decrease) in comparison with the other treatments (P£0.05). Strain UTPF86 was more effective than the other treatments in control of the said nematode (P£0.05).

In the course of the present study, samples were taken from the non-defoliant strain of Verticillium dahliae (SS-4) from infected olive groves in Toshan area in Southern Gorgan. Root-knot nematode, Meloidogyne javanica, was recovered from infested olive seedlings and after identification was reaned on tomato seedlings cv. Rutgers. During the study, one-year-old seedlings of olive cultivars Zard, Roghani, Koroneiki (resistant to verticilliosis) vs. Manzanilla (sensitive to verticilliosis), were transplanted to pots containing 2000 g of sterilized sandy loam soil. The experimental study was conducted in a completely randomized design of 32 treatments and five replications. Treatments consisted of: control, mere nematode, fungus alone, and fungus+nematode. Pots were inoculated with (2000, 3000, 4000) J2 of the nematode and/or (10 no/g soil) microsclerotia of fungus as according to the treatments. Pots were placed on glasshouse benches at a temperature of 25-27oC and in natural light. The experiment was terminated after 10 months past with the following parameters determined: fresh weight of root and stem, no. of galls and egg masses per each root system, percentage of incidence of symptom on aerial parts, browning of vascular tissue, decrease in seedling height and stem/root tissue colonization by the fungus. Results indicated that presence of nematode caused reduction in colonization of the fungus in the root and stem and vice versa, meaning that presence of fungus caused reduction in no. of galls and egg masses produced by the nematode. This was when a maximum percentage of disease symptoms on aerial parts was observed in fungus+nematode treatments. Severe fungal wilt on aerial parts of Zard cultivar was observed in fungus+nematode treatments and mild fungus wilt was observed in mere fungus treatments and in the case of Koroneiki cultivar. The reduction of gall and egg mass production in root system occurred respectively in cvs. Manzanilla, Zard, Roghani and Koroneiki cultivars (p£0.05).

Insect natural enemies selected for such specific traits as faster developmental times, longer survivor, increased fecundity, and larger body size might be considered during production of biological control agents in certain situations. For instance, traits related to developmental rates may be selected for, if genetically based variation exists within temperature-dependent responses. Hippodamia variegata (Goeze) (Col: Coccinellidae) is one of the most important predators of orchard pests in Iran. In the course of this study, the effect of six constant temperatures i.e. 17.5, 22.5, 25, 27.5, 30 and 32.5oC on preimaginal development and mortality of this predator, feeding on Angoumois grain moth, Sitotroga cerealella Olivier (Lep. Gelechiidae) and common pistachio psylla, Agonoscena pistaciae Burckhardt as well as Lauterer (Hem.: Aphalaridae) was evaluated under laboratory conditions (55±5% r.h. and a 16:8 h of photoperiodism). Temperature exerts a great effect on the development and the level of feeding of Hippodamia variegata. Total developmental times at the above-mentioned temperatures were 47.63±1.53, 25.08±0.18, 17.27±0.64, 15.14±0.37, 12.16±0.64 and 11.27±0.39 days on S. crealella vs., 40.11±0.75, 22.68±0.32, 18.6±0.36, 15.5±0.18, 13.9±0.31, and 13.12±0.51 on A. pistaciae, respectively, indicating a significant decrease of developmental time with increase in temperature. Minimum survival rate was recorded for first nymphal instar whereas the survival at third and forth instars along with pupa amounted to a maximum at the above-mentioned temperatures. The results showed significant differences among the six temperatures as regards developmental times. The estimated lower temperature threshold and thermal constant for the entire developmental times, using the ordinary linear model, were estimated. The lower developmental thresholds (To) of egg, larva, pupa and egg to adult emergence were estimated through linear regression equation to be 11.91, 12.43, 9.63 and 10.31oC respectively. The thermal constants required at the above mentioned periods were estimated as 39.06, 156.25, 57.8 and 285.71, respectively.

The carob moth, Ectomyelois ceratoniae (Zeller), (Lep.: Pyralidae), is an importantly injourious pest on a wide range of plants throughout the world and as well a major pest of pomegranate orchards in Iran. Insight into the sexual behavior of an insect is indispensable for optimizing the application of pheromone in pest control strategies and while information on reproductive behavior being the prerequisite to the chemical ecology studies. In Moths, the blend ratio of sex pheromone components as well as pheromone communication system in different areas can vary depending upon due to adaptation to varying environmental conditions and on host plants. In the course of this research, sexual behavior as well as male cross-attraction between individuals from Saveh, Arsanjan and Kerman populations were examined in wind tunnel and under laboratory conditions (27±1oC and 60±10% relative humidity, light intensity of approximately 10 lux and 0.3 m/sec of wind velocity), using two day-old calling virgin females as the source of pheromone. The results indicated that the adults began to mate starting from the first night following eclosion, with males starting the search behavior. Most males employed in the study took flight after being released in the wind tunnel. The percentages of males from Saveh, Arsanjan and Kerman populations that contacted the pheromone source were 83.3, 76.9 and 85.7% respectively. Data analysis revealed no discrimination (among test populations’ males) between female from their own population vs. females from other populations. This result reflects the fact that possible differences in pheromone blend among populations of E. ceratoniae did not prevent cross-attraction under laboratory conditions. Insight into the sexual behaviors and an identification of the interfering factors can be of practical importance for the development of integrated pest management systems in pomegranate orchards in Iran.

Root colonization by antagonist bacteria has been considered as a prerequisite for a successful biocontrol. For an effective suppression of plant disease, an efficient and fast colonization is necessary to prevent the establishment of pathogen on the root system. Colonization of canola root by strain UTPF86 were investigated with and without Rhizoctonia solani AG-4, under greenhouse conditions. Among 14 strains of Pseudomonas fluorescens, strain UTPF86 was selected on the basis of biocontrol and root colonization activity. Chloramphenicol and tetracycline resistant mutants of this strain, were used in all experiments. The roots were sampled at 1, 2, 3 and 4 weeks after planting. Bacterial population was determined using dilution procedure. Bacteria enumerated on selective S1 medium. This study demonstrated that in the presence of R. solani, root colonization was significantly increased by strain UTPF86. Furthermore, the rate of root colonization increased during the first two weeks and then it began to decrease during the third and fourth weeks post planting.

Herbivory is observed in different forms, one of these forms leading to gall production. Among gall–inducing insects, oak gall wasps (Hymenoptera: Cynipidae) are found on the oak trees producing galls on certain parts of the host. In this survey, oak gall wasps were collected from oak forests in West Azerbaijan in spring (2010). The occurred galls on oak trees (in spring) were collected from such locations as Ghabre-hosein, Mirabad, Vavan, Shalmash, Rabat and Dar-ghabr (a number of 40 trees in each site). In each tree, as a unit of sampling, all the occurred galls on 4 branches (each branch of 40 cm length, and each in any of the 4 geographical directions) were counted. Species richness was evaluated through Rarefaction and Jackknife methods and four similarity indexes calculated. During the survey, 7 oak gall wasp species (sexual generation) were indentified on oaks (Quercus infectoria, Q. brantii and Q. libani) in West Azerbaijan. Most of the galls occurred on Q. brantii. All collected oak gall wasps belonged to 3 genera, namely: Andricus, Chilaspis and Biorhiza. The highest number of expected species’ richness as determined through Rarefaction and Jackknife methods was estimated at 4.68 and 5.2 species respectively, in Mirabad region. The highest similarity indexes of Morisita, Horn, Renkonen and Sorensen were recorded between Ghabre-hosein and Mirabad in the sexual generation of oak gall wasp species. Difference in the local distribution of oak species (Quercus sp.) and subspecies shall be considered as one main factor involved in species diversity, and as well in the oak gall wasp species’ distribution in different locations under study.

Thirty seven isolates of Magnaporthe grisea collected from several host plants from family of Poaceae namely Digitaria singuinalis, Setaria italica, and Echinochloa sp. were tested for their pathogenecity against two susceptible rice cultivars. Conidial suspensions were prepared by the surfaces of 14-day-old cultures being washed with sterile water and adjusting the final concentrations to approximately 5×104 conidia per ml with the aid of hematocytometer. Inoculums were applied to the leaves of 3 week-old plants and symptoms scrutinized 10 to 12 days following inoculation. Moreover, to confirm the outcomes of the test, the survey of the infection of the leaves was recapitulated after a 5 days interval. Pots each containing sixty seedlings of either Binam or Tarom rice cultivars were sprayed with 50 ml suspension of 5×104 conidia per ml from either pure cultures of the M. grisea or water, with a hand-held mist sprayer (until runoff) onto rice plants that were at a four-to-five-leaf stage. Inoculated plants were incubated in a humidity chamber and maintained at 100% relative humidity (RH) for 48 h and then reincubated in a greenhouse (20 to 24oC). Also negative and positive control plants were sprayed with distilled water and with rice infecting isolate respectively in the same manner. After 10 to 12 days past, leaf spot symptoms appeared on some inoculated plants. Then five virulent and semi virulent isolates as based upon their interaction with rice were analyzed for pathogenic races. In total 13 cultivars and lines (eight varieties differentiated through international standard cultivars and five through Near Isogenic Lines (NILS)) were examined. The last five isolates were classified in four pathogenic races IB-58, IA-27, IA-127, IA-17 that belonged to two race groups IA and IB as based on their virulence on eight international differential varieties, and in A, B, C, D as based on their virulence on five Near Isogenic Lines (NILS).